Process of treating waste sulfite liquor.



WALTER H. DICKERSON, OF MUSKEGON, MICHIGAN, ASSIGNOR T0 TANNING EXTRACTCOMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PROCESS OF TREATING WASTE SULFITE LIQUOR.

No Drawing.

To all whom it may concern:

. When these are treated in accordance with liquor.

the hereinafter described invention, a tanning extract which will tanperfectly white or nearly white results.

By the preferred treatment I take waste sulfite liquor, either .as itcomes from the digesters or preferably after it has been concentrated in'vacuo to a consistency say of about 25 Baum, and add thereto chlorid ofsodium or a similar salt to the extent'of about 10 to 25% by Weight ofthe concentrated liquor. This addition of salt should be made preferablyin a grinding or crushing apparatus, in' which the salt in a finelypulverized state is mixed very intimately with the liquor. The liquorsoon gelatinizes into a thick, heavy, pasty mass, which becomes quitesolid upon standing a few hours. Upon standing for a longer period, sayfrom at to 48 hours, it changes from a dark to a light color and losesits thick, solid nature becoming of a much thinner consistency. Uponadding water it Will be found that this light colored mass of thinconsistency has entirely taken up the salt which is either combined withor dissolved in the evaporated Of course, there are certain limitswithin which the proportion of salt to be i added may be varied, andwherein the described effect will be obtained. With the higherproportions of salt named, a tanning extract is produced which giveswhite leather, whereas the smaller proportions of salt produce leatherwhich is not so light 1n color. 10% of salt is sutficient to make theliquor available as a tanning extract but does not invariably produce aslight a colored leather as higher percentages. It requires from 20 to25% to invariably produce white or nearly white tannage with pickledskins.

When the salt is added, as is preferable, to waste sulfite liquors whichhave been pre- Specification of Letters Patent.

Patented Nov. 5, 1912.

Application filed May 25, 1909. Serial No. 498,304.

viously concentrated, the resulting lightcolored mass requires theaddition of waste in order to make it suitable for use as a tanningextract. It is economical and advantageous to ship the product in thisconcentrated condition, and it is afterward diluted with water to bringit to the proper specific gravity for tanning. The dilution with waterwill be in such proportion as to bring the resulting extract to adensity of 2 to 3 Baum; and the proportion in which water will have tobe added for this purpose will be approximately one part of water tothree or four parts of concentrated, treated liquor. When the' water isadded and the whole mass is intimately commingled, a certain amount ofgas is evolved. The extract so obtained has been found to beparticularly adapted to the tanning of pickled skins. Other salts orcompounds, such for instance as calcium chlorid, potassium chlorid ormagnesium chlorid, which producesiniilar effects when added to theliquors, may be used; butup to the present time, common salt or sodiumchlorid has been found to give the best results and to be most practicalcommercially. My invention includes, broadly considered, the use ofanyelectrolyte which will produce similar effects to those previouslyherein described as attained by the use of sodium chlorid, and I do notcon fine myself to the use of this salt or of any other of the saltsmentioned either singly or in combination.

I have found that when two to three parts of the thick tanning extractproduced by this process are mixed with one part of the thinunevaporated liquor made by the use of oxalic acid or of a similarnon-decomposing precipitant for lime the combined liquor possessesdecided plumping properties and gives a soft leather. These proportionsmay be varied and I instance it simply as an example.

The tanning extracts obtained by the procedure first described areparticularly suitable for retanning previous to dyeing, in which casequalities are imparted to the skins which are similar to those obtainedby a mordant or to those of skins which have been treated to acolor-bottom.

When the tanning material is prepared by the latter procedure it isparticularly adapted to the tannin of een skins. I have found, also,that y using a thin, unevaporated liquor which has been treated withchrome alum instead of oxalic acid, the same results, or practically thesame, will be produced. Thetanning agent thus 'made also imparts a plumpdense quality to the leather, and at the same time makes it soft andflexible.

I am unable to definitely state the reactions that take place in any ofthese combinations, owing to the complicated nature of the sulfiteliquors.

As I have already stated, I prefer to add the salt to the waste liquorsafter the same have been concentrated. But such addition can be made tothe liquors as received from the digcsters, and in relatively the sameproportion as that hereinbefore set forth, whereupon the mixture maythen be evaporated down to the aforesaid consistency of say 25 Baum, ifdesired, for shipment. IVhen the salt or an equivalent compound is thusadded to the thin unconcentrated liquor it does not, of course, changeinto a thick pasty mass and later to a lighter colored mass of thinconsistency unless it 'is concentrated. The thin liquors, however, clearup somewhat, and-gas, apparently sulfur dioxid, is evolved.

Instead of waiting the specified period of 24 to 4-8 hours, thehereinbefore described effects can be quickly attained by subjecting thesalted concentrate to a slight elevation of temperature. There is thusproduced a tanning extract'in a minimum of time, having substantiallythe same property as that slowlydeveloped as-before described. Thedigestion with the salt, as I prefer'to term it, may,therefore, occurwhile the liquors are hot or cold.

The tanning extracts produced by this process are found, when applied tohides previously plumped with sulfuric acid, to preserve a very largepercentage of said lumping and to produce a light-colored, soft andflexible leather.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent, is

p 1. In the manufacture of tanning extracts from waste sulfite liquor,the admixture and digestion of the liquor with a sutlicient quantity'bfan electrolyte capable of gelatinizing the liquor when concentrated.

2. In the manufacture of tanning extracts from waste sulfite liquor, theadmixture and digestion of the liquor with a sufficient quantity of anelectrolyte capable of converting it, when concentrated, to a lightcolored mass of thin consistency. I

3. In the manufacture of tanning extracts from waste sulfite liquor, theadmixture and digestion of the liquor with a sufficient quantity ofsodium chlorid to gelatinize the liquor when concentrated. Y

4. In the manufacture of tanning extracts from waste sulfite liquor. theadmixture and digestion of the liquor with a sufiicient quantity ofsodium chlorid to convert it, when concentrated, to a light-colored massof thin consistency.

5. In the manufacture of-tanning extracts from waste sulfite liquor; theadmixture and digestion of the liquor with a sutficient quantity of vanelectrolyte capable of converting it, when concentrated. to alight-Coloredmass of thin consistency, and the later addition thereto ofa thin. tanning extract made by the addition of a non-decomposingprecipitant for lime to waste sulfite'liquor.

6. A tanning extract obtained from waste sulfite liquor which consistsof a light-colored mass of thin consistency when concentrated to aspecific gravity of about 25 Baum.

In testimony whereof I afiixmy signature in presence of two witnesses.

WALTER H. DICKICRSON. IVitnesses C. B. SCIIROEDER, R. G. DUBOIS.

